A great many drip emitter systems have been designed, develop and patented. They find wide commercial acceptance, especially by plant growers in areas of limited water supply, since they can be designed to deliver to each plant adequate water with minimal waste. However, such systems are plaqued by a variety of problems. For example, variations in the pressure of the water supplied to the drip emitter heads usually causes substantial variations in the amount of water delivered to the plant. This, in turn has a significant practical effect. Since the tubing used to deliver the water to the plant increases in price as it increases in size, it is desirable economically to use relatively small diameter tubing. However, because internal frictional losses are significant for such tubing, even at low pressures, the pressure at the inlet end of the water line which includes the emitters, that is, the end of the tubing adjacent the water manifold, will be significantly higher than the pressure at the far end of the line. Since the water delivered by prior drip emitters varies with water pressure, plants adjacent the inlet end of the line will receive substantially more water than plants adjacent the far end. While it would be very desirable to provide a drip emitter that delivered the same water at the same rate regardless of internal water pressure, insofar as is known to the inventor, before the emitter and system herein described no such structure had been developed. Further, since the per acre cost of a drip emitter system is quite significant, it is very desirable to simplify the emitter structure as much as possible, consistent with its operational objectives. Also, it is very desirable to provide an emitter structure that is relatively uneffected by sediment and debris in the water. Some prior emitter systems have incorporated a self-cleaning feature. However, their per unit cost is quite substantial. In addition, since the emitter system is taken up while the field is being prepared for the next crop, it would be very desirable to achieve an emitter system that could be easily coiled for compact storage, and then subsequently reinstalled without requiring considerable fiddling and adjustment to render it again usable.
The present invention has, as primary objectives, the provision of a drip emitter head and system that is simple and of relatively low cost, one that will emit a substantially constant volume of water over a wide variation in internal water pressure, one which is self-cleaning if desired, and one which can be coiled, stored and reinstalled without much adjustment to render it operative. These and other objects of the invention will appear to one skilled in this art from the following description of preferred embodiments.